Combined data on plant species abundance and composition from LTER and other grasslands in the United States, 1943 - 2010

Understanding how biotic mechanisms confer stability in variable environments is a
fundamental quest in ecology, and one that is becoming increasingly urgent with global
change. Several mechanisms, notably a portfolio effect associated with species richness,
compensatory dynamics generated by negative species covariance and selection for stable
dominant species populations can increase the stability of the overall community. While the
importance of these mechanisms is debated, few studies have contrasted their importance in
an environmental context. We compiled nine long-term datasets of grassland species
composition to evaluate the strength of biotic mechanisms of community stability and assess
how these mechanisms change across precipitation gradients. Data were collected in replicate
plots over time at nine different sites throughout the US (replicates within a site range
from 5-100, plot sizes from 0.1 m² to 17 m²; minimum 9 years, maximum 30 years). Species
abundance was measured as either percent cover, biomass, or allometrically-derived biomass.
At all sites the measurement techniques and management regimes remained constant over the
collection period, and the data collection methods were not relativized. For example, sites
in which species composition were measured as percent cover do not require their estimates
to sum to 100. For sites with long-term experimental treatments, only the control plots were
included. These data have been presented in: Lauren M. Hallett, Joanna S. Hsu, Elsa E. Cleland,
Scott L. Collins, Timothy L. Dickson, Emily C. Farrer, Laureano A. Gherardi, Katherine L.
Gross, Richard J. Hobbs, Laura Turnbull, Katharine N. Suding. 2014. Biotic mechanisms of
community stability shift along a precipitation gradient. Ecology 95:1693–1700. http://dx.doi.org/10.1890/13-0895.1